The present invention relates to a refrigeration circuit for circulating a refrigerant in a predetermined flow direction through at least one functionally disconnectable component, the refrigeration circuit comprising in flow direction an expansion device, an evaporator, a compressor, and a heat-rejecting heat exchanger, wherein an upstream-side shut-off valve is provided upstream of the component and a downstream-side shutoff valve is provided downstream of the component.
Refrigeration circuits of different kinds using single or multi-component refrigeration media, operating in normal or supercritical modes, etc. are well known to a person skilled-in-the-art.
Refrigeration circuits comprises—in flow direction—a compressor, a heat-rejecting heat exchanger (which may be gas cooler/condenser), an expansion device (e.g. a throttle valve) and an evaporator. The German patent application 10 2004 038640 discusses a refrigeration circuit according to the state of the art.
Furthermore, a refrigeration circuit according to the state of the art will be explained with respect to the enclosed FIG. 1.
The refrigeration circuit 1 as shown in FIG. 1 can be used for example for supermarket or industrial refrigeration. In flow direction the refrigeration circuit 1 comprises a compression stage, consisting of two or more compressors 2, 2′ arranged in parallel. Each of these compressors 2, 2′ comprises a suction-side shut-off valve 3, 3′ as well as a discharge-side shut-off valve 4, 4′.
Via conduit 5 the compressed refrigerant is led to a gas cooler/condenser 6, in which the refrigerant is cooled or liquefied, respectively. Subsequent to the gas cooler/condenser 6 a receiver 8, to which the refrigerant is led via conduit 7, collects and stores the refrigerant for subsequent delivery—via conduits 9, 10 and shut-off valve a′—to one or a plurality of throttle valves b, b′ of one or a plurality of refrigeration consumer(s). Via conduit and pressure relief valve 16 gaseous refrigerant can be withdrawn from the receiver 8.
Connected to each throttle valve b, b′ is an evaporator 12, 12′. Via conduits 11, 13, 15 and shut-off valve c′ the evaporator outlets 12, 12′ are connected to the entrances of the compressors 2, 2′.
In FIG. 1 an arrangement of two or more throttle valves b, b′ and evaporators 12, 12′ is shown. Via conduits 10′ and 11′ further throttle valves and evaporators can be connected to this arrangement. Via conduits 9′ and 13′ at least one additional evaporator and/or at least one additional arrangement of two or more evaporators can be connected to the refrigeration circuit 1.
During the service life of a refrigeration circuit, some components, e.g. the refrigeration consumer (i.e. expansion device and evaporator), heat exchanger, compressor, or other, of the refrigeration circuit may need to be functionally disconnected, e.g. for service. As used herein, the term “functionally disconnected” has the meaning that the component is no longer in fluid communication with the refrigerant flow path of the refrigeration circuit, although it may physically still be located within the refrigeration circuit. It is known to provide functionally disconnectable components comprising an upstream-side shut-off valve and a downstream-side shut-off valve; that way the component may be disconnected from the system. It is also known to provide at least two of the components in question in parallel; in case of replacement or maintenance of one component the other component continues to operate and is able to take over the task of the component being out of order or switched off. After being functionally disconnected these components are no longer in fluid communication with the system's safety valves and refrigerant within the functionally disconnected component may expand leading to increased pressure which is a safety concern.
For example, in case of service maintenances of throttle valves b, b′ or evaporators 12, 12′ the afore-mentioned shut-off valves a′ and c′ enable the disconnection of throttle valves b, b′ and evaporators 12, 12′ from the refrigeration circuit. Firstly, shut-off valve a′ has to be closed to stop the flow of refrigerant via lines 9 and 10 to the evaporators 12, 12′. Now it has to be waited for approximately 10 to 15 minutes until shut-off valve c′ can be closed to allow all liquid refrigerant within the evaporators 12, 12′ to be vaporized and sucked off the evaporators 12, 12′ by the compressors 2, 2′.
Unfortunately, it happens, that both shut-off valves a′ and c′ are closed simultaneously or that shut-off valve c′ is closed too early by a service person. As a result the remaining liquid refrigerant within the evaporators 12, 12′ vaporizes. This raises the pressure within the evaporators 12, 12′ and the conduits 10, 11 between the evaporators 12, 12′ and the shut-off valves a′ and c′ to a level the material of the evaporators 12, 12′ and the conduits 10, 11 might not be able to withstand.
Especially, when so-called high-pressure refrigerants, for example CO2, are used, either the material of the evaporators 12, 12′ or the conduits 10, 11 have to withstand pressures up to 80 bar, resulting in an increase of the investment costs of the material used for the evaporators 12, 12′, the conduits 10, 11, the throttle valves b, b′ and the shut-off valves a′ and c′. According to the state of the art the shut-off valves a′ and c′ can be designed as three-way-valves, each being connected to a pressure control device, e.g. a pressure relief valve. As soon as the pressure within the evaporators 12, 12′ and the conduits 10, 11 exceeds a determined pressure value, the vaporized refrigerant is led via at least one of these three-way-valves and pressure relief valves to the atmosphere or into a closed space. Especially the blow-off of refrigerant into a closed space might be harmful or hazardous. It is obvious, that both aforementioned solutions result in an unwelcome loss of refrigerant.
Accordingly, it is an object of the present invention to provide a refrigeration circuit, which avoids the afore-mentioned problems.